Active layer based on polymer aggregation structure regulation and preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of active layers, and particularly relates to an active layer based on polymer aggregation structure regulation and a preparation method and application thereof. Comprising the following steps: S1, reacting chlorobenzene with 2-bromothiophene according to a ratio of (10-n): n (0lt; n is less than or equal to 10) to obtain a mixed solvent; s2, mixing and stirring the mixed solvent and the donor powder to obtain a donor precursor solution; s3, preparing an acceptor precursor solution; and S4, sequentially spin-coating the donor precursor solution and the acceptor precursor solution to prepare the active layer film. The active layer is prepared by accurately regulating and controlling a polymer aggregation structure through an optimized solvent, efficient internal exciton dissociation and charge collection are realized, and the active layer film is applied to a solar cell device or an organic light-emitting diode device, so that the overall performance of the device can be remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of active layers, and particularly relates to an active layer based on the regulation of polymer aggregation structure, and a preparation method and application thereof. Background Art

[0002] Organic solar cells (OSCs) have unique advantages such as light weight, flexibility, low-cost solution processing, and weak light response, and are particularly suitable for emerging fields such as wearable devices and building-integrated photovoltaics. Among them, the layer-by-layer preparation method (LBL) has attracted much attention because it can precisely regulate the vertical distribution of donors and acceptors and avoid uncontrollable phase separation in bulk heterojunction blends. By sequentially depositing donors and acceptors, this method can achieve a more controllable interfacial morphology and a more optimized charge transport path. However, the inherently low dielectric constant of organic semiconductors results in a relatively high exciton binding energy (about 0.3 - 0.5 eV), which makes carrier separation strongly dependent on the molecular-level contact at the donor-acceptor interface. At the same time, the crystallization kinetics induced by solvent evaporation during the solution processing is difficult to control, and it is easy to form grain boundary defects and trap states, resulting in significant trap-assisted recombination losses (the non-radiative recombination rate can reach 10 6 s -1 order of magnitude). The combined effect of these physical processes poses a great challenge to the regulation of the active layer morphology, and there is an urgent need to develop new solvent engineering strategies to precisely regulate the crystallization kinetics and interfacial properties.

[0003] Regarding the above problems, researchers have tried various improvement strategies. Volatile solid additives (such as 1,4-diiodobenzene) can optimize the molecular arrangement through heat treatment, but there is a risk of incomplete volatilization, which in turn affects the long-term stability of the device. Although the solvent method can regulate the film-forming kinetics, its optimization effect is mainly limited to the bulk heterojunction system, and there is insufficient targeted regulation for different layers in the LBL process. It is often difficult to form an ideal microstructure in the active layer. Although these methods have improved the device performance to a certain extent, they still have not fundamentally achieved the coordinated optimization of crystallization defects and interfacial compatibility in the active layer, resulting in limited efficiency increase of LBL-OSCs, and the fill factor is generally lower than 80%, which has become the key bottleneck restricting further performance improvement. Summary of the Invention

[0004] The technical problems to be solved by this application are as follows: 1. The crystallization kinetics induced by solvent evaporation during the solution processing of the active layer of an organic solar cell or diode is difficult to control, and it is easy to form grain boundary defects and trap states; 2. There is insufficient targeted regulation for the donor or acceptor layer in the LBL process, and it is difficult to fundamentally achieve the coordinated optimization of crystallization defects and interfacial compatibility in the active layer, resulting in limited efficiency increase of LBL-OSCs.

[0005] To solve the above technical problems, the present application provides the following technical solutions: A method for preparing an active layer thin film, comprising the following steps:

[0006] S1 Prepare a donor precursor solution;

[0007] S2 Prepare an acceptor precursor solution;

[0008] S3 Spin-coat the donor precursor solution and the acceptor precursor solution in sequence to obtain an active layer thin film.

[0009] Further, the solvent of the donor precursor solution is prepared by mixing chlorobenzene and 2-bromothiophene in a volume ratio of 10 - n:n; wherein, 0 < n ≤ 10.

[0010] Further, the donor includes D18, 4CzFCN; the acceptor includes L8-BO, TPBi.

[0011] Further, the concentration of the donor in the donor precursor solution is 8 ± 0.4 mg / mL, and the concentration of the acceptor in the acceptor precursor solution is 9.6 ± 0.6 mg / mL.

[0012] Further, the mixing and stirring temperature in step S1 is 100 °C; the mixing and stirring temperature in step S2 is room temperature.

[0013] Further, the thickness of the photoactive layer is 100 nm ± 10 nm.

[0014] Further, the solvent of the acceptor precursor solution includes chloroform (CF).

[0015] Further, the acceptor precursor solution further contains 0.5 vol% 1-chloronaphthalene.

[0016] An organic solar cell, which is composed of a conductive substrate, a hole transport layer, a photoactive layer, an electron transport layer, and a metal electrode, and the photoactive layer is the above-mentioned active layer thin film.

[0017] Further, when preparing the active layer of the organic solar cell, the solvent in the donor precursor solution is prepared by mixing chlorobenzene and 2-bromothiophene in a volume ratio of 6 - 9:4 - 1.

[0018] As a preferred embodiment of the solar cell of the present invention, the active layer is composed of D18 and L8-BO.

[0019] As a preferred embodiment of the solar cell of the present application, wherein: when preparing the active layer of the organic solar cell, the solvent in the donor precursor solution is prepared by mixing chlorobenzene and 2-bromothiophene in a volume ratio of 8:2.

[0020] As a preferred embodiment of the solar cell described in the present application, when preparing the active layer of the organic solar cell, the concentration of D18 in the donor precursor solution is 8 mg / mL, and the concentration of L8-BO in the acceptor precursor solution is 9.6 mg / mL. The donor precursor solution is heated at 100 °C, and the acceptor precursor solution is stirred at room temperature.

[0021] As a preferred embodiment of the solar cell described in the present application, the thickness of the photoactive layer is 100 nm.

[0022] As a preferred embodiment of the solar cell described in the present application, wherein: the conductive substrate is an ITO substrate, the hole transport layer is composed of PEDOT:PSS, the electron transport layer is composed of PDIN, and the metal electrode is an Ag electrode.

[0023] As a preferred embodiment of the solar cell described in the present application, wherein: the PEDOT:PSS solution is spin-coated on the ITO substrate at 5000 rpm, and then annealed at a temperature of 150 °C for 15 min to obtain the hole transport layer.

[0024] As a preferred embodiment of the solar cell described in the present application, wherein: a 1.0 mg / mL PDIN solution is spin-coated at a speed of 3000 revolutions per minute for 20 s to obtain the electron transport layer.

[0025] As a preferred embodiment of the solar cell described in the present application, wherein: the metal electrode is an Ag electrode, and the thickness of the Ag electrode is 100 nm.

[0026] An organic light-emitting diode (OLED) device, which is composed of a conductive substrate, a hole transport layer, an active layer, an electron transport layer, and a metal electrode; the active layer is the above-mentioned active layer thin film.

[0027] The conductive substrate is an ITO substrate; the hole transport layer is composed of PEDOT:PSS; the active layer is composed of 4CzFCN and TPBi; the electron transport layer is composed of LiF; the metal electrode is an Al electrode.

[0028] The beneficial effects of the present invention:

[0029] The present invention uses a mixed solution of 2-BrTh or 2-BrTh and CB as the solvent for donors (such as D18, 4CzFCN), which can make the morphology of the active layer smoother, enable the acceptor to penetrate more into the donor, form a good vertical structure, and is beneficial to improving the collection of excitons and charges inside the device. The experimental results also prove this point. After introducing 2-BrTh with a volume fraction of 20% into CB, the device of the D18(CB+2-BrTh) / L8-BO(CF) system achieves a PCE of 19.52% and an FF of 80.17%. In terms of stability, the introduction of 2-BrTh can also improve the device stability, increasing the probability of commercial development. It has been found through research that if a suitable solvent is used to assist in spin-coating layer by layer, the morphology of the active layer can be accurately controlled. Description of the Drawings

[0030] Figure 1 EQE curves of the devices of Comparative Example 1 and Example 2;

[0031] Figure 2 Stability test results of the devices of Comparative Example 1 and Example 2 under continuous light illumination;

[0032] Figure 3 (a) Open-circuit voltage, (b) short-circuit current vs. light source intensity, (c) TPC, (d) TPV of the devices of Comparative Example 1 and Example 2;

[0033] Figure 4 (a, b) Photo-CELIV, (c) DOS, and (d) carrier mobility of the devices of Comparative Example 1 and Example 2;

[0034] Figure 5 Experimental result diagrams of (a) CB and (b) CB+20% 2-BrTh dissolving D18;

[0035] Figure 6 (a, b) UV-visible absorption spectra of D18 and (c) D18 / L8-BO after treatment with CB and CB+20% 2-BrTh, (d) PL curve of D18 after treatment with CB and CB+20% 2-BrTh;

[0036] Figure 7 (a) Time-dependent contour maps of in-situ UV-visible absorption spectra of D18(CB) and (b) D18(CB+2-BrTh) films during spin-coating; (c) UV-visible absorption curves of D18(CB) and (d) D18(CB+2-BrTh) at different times (e) Time evolution of the peak position and intensity of D18(CB) and (f) D18(CB+2-BrTh) films during spin-coating;

[0037] Figure 8 (a) Time-dependent contour plots of in-situ UV-Vis absorption spectra of D18(CB) / L8-BO and (b) D18(CB + 2-BrTh) / L8-BO thin films during spin coating; (c) UV-Vis absorption curves of D18(CB) and (d) D18(CB + 2-BrTh) at different times; (e) Absorption spectra of D18(CB) / L8-BO and (f) D18(CB + 2-BrTh) / L8-BO thin films at different times;

[0038] Figure 9 AFM topography images of D18 thin films treated with CB and CB + 20% 2-BrTh;

[0039] Figure 10 Three-dimensional topography images of D18 / L8-BO thin films and L8-BO(CF) thin films treated with CB and CB + 20% 2-BrTh;

[0040] Figure 11 J-V curves for D18(CB) / L8-BO and D18(CB + 20% 2-BrTh) / L8-BO devices

[0041] Figure 12 OLED device structure diagram;

[0042] Figure 13 EQE-current density curves for the OLED devices of Example 5 and Comparative Example 2;

[0043] Figure 14 AFM image of the thin film prepared by dissolving 4CzFCN in CB as the solvent and spin coating;

[0044] Figure 15 AFM image of the thin film prepared by dissolving 4CzFCN in 2Br-Th as the solvent and spin coating. Detailed implementation manners

[0045] To make the above objects, features, and advantages of the present application more obvious and understandable, the following will describe the detailed implementation manners of the present application in conjunction with the accompanying drawings of the specification.

[0046] In the following description, many specific details are set forth to facilitate a thorough understanding of the present application. However, the present application may be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0047] Second, the "one embodiment" or "embodiment" referred to herein means a specific feature, structure or characteristic that may be included in at least one implementation manner of the present application. The "in one embodiment" that appears in different places in this specification does not all refer to the same embodiment, nor is it an individual or selectively mutually exclusive embodiment with other embodiments.

[0048] Embodiment 1

[0049] This embodiment provides an organic solar cell, and the device structure is ITO / PEDOT:PSS / D18 / L8-BO / PDIN / Ag in sequence, which is prepared by the following steps:

[0050] A1-1: After the back of the ITO is marked, it is ultrasonically cleaned in 2% ITO cleaning solution, deionized water, isopropanol, and ethanol for 15 min in sequence, dried at 60 °C, and then treated with ultraviolet ozone for 3 min.

[0051] A1-2 Hole transport layer: After filtering PEDOT:PSS, it is dropped and coated on the surface of the ITO, spin-coated at 5000 rpm for 30 s (film thickness ≈ 20 nm), annealed in air at 150 °C for 15 min, and transferred to a nitrogen glove box for standby.

[0052] A1-3 Solution preparation: The mixed solvent is prepared from chlorobenzene and 2-bromothiophene according to a volume ratio of 9:1 (v / v) (CB + 10% 2-BrTh). Subsequently, D18 is dissolved in this mixed solvent at a concentration of 8 mg / mL; L8-BO is dissolved in chloroform containing 0.5 vol% 1-chloronaphthalene (9.6 mg / mL), and all solutions are stirred for ≥ 1 h before spin coating.

[0053] A1-4 Spin coating the active layer: Spin coat the donor precursor solution and the acceptor precursor solution in sequence, and then place it in a transfer chamber and pump it to negative pressure (≤ 10 -4 MPa), and process for 2 minutes to obtain an active layer film about 100 nm thick.

[0054] A1-5 Electron transport layer: After stirring the solution of N,N'-diisopropylaminoperylene tetracarboximide (PDIN) / trifluoroethanol (1.0 mg / mL) at room temperature, spin coat it into a film at 3000 rpm.

[0055] A1-6 Electrode evaporation: Evaporate Ag (thickness 100 nm) in a vacuum of 5 × 10 -4 Pa, and the effective area of the device is 0.04 cm2.

[0056] Embodiment 2

[0057] The difference between Embodiment 2 and Embodiment 1 is that the mixed solvent is prepared from chlorobenzene and 2-bromothiophene according to a volume ratio of 8:2 (v / v) (CB + 20% 2-BrTh), and the others are the same as Embodiment 1.

[0058] Example 3

[0059] The difference between Example 3 and Example 1 is that the mixed solvent is prepared from chlorobenzene and 2-bromothiophene at a volume ratio of 7:3 (v / v) (CB + 30% 2-BrTh), and the others are the same as in Example 1.

[0060] Example 4

[0061] The difference between Example 4 and Example 1 is that the mixed solvent is prepared from chlorobenzene and 2-bromothiophene at a volume ratio of 6:4 (v / v) (CB + 40% 2-BrTh), and the others are the same as in Example 1.

[0062] Comparative Example 1

[0063] This Comparative Example 1 provides an organic solar cell, and the device structure is successively ITO / PEDOT:PSS / D18 / L8-BO / PDIN / Ag, which is prepared by the following steps:

[0064] A5-1: After the back surface of the ITO is marked, it is successively ultrasonically cleaned in 2% ITO cleaning solution, deionized water, isopropanol, and ethanol for 15 min, dried at 60 °C, and then treated with ultraviolet ozone for 3 min.

[0065] A5-2 Hole transport layer: After filtering PEDOT:PSS, it is dropped and coated on the surface of the ITO, spin-coated at 5000 rpm for 30 s (film thickness ≈ 20 nm), annealed in air at 150 °C for 15 min, and transferred to a nitrogen glove box for use.

[0066] A5-3 Solution preparation: D18 is dissolved in chlorobenzene (CB) (8 mg / mL); L8-BO is dissolved in chloroform containing 0.5 vol% 1-chloronaphthalene (9.6 mg / mL), and all solutions are stirred for ≥ 1 h before spin coating.

[0067] A5-4 Electron transport layer: After stirring the PDIN / trifluoroethanol (1.0 mg / mL) solution at room temperature, it is spin-coated into a film at 3000 rpm.

[0068] A5-5 Electrode evaporation: Evaporate Ag (thickness 100 nm) in a vacuum of 5×10 -4 Pa, and the effective area of the device is 0.04 cm 2 .

[0069] Example 5

[0070] This example provides a preparation method of an organic light-emitting diode (OLED) device, and the device structure is successively ITO / PEDOT:PSS / 4CzFCN / TPBi / LiF / Al, which is prepared by the following steps:

[0071] A6-1: After the ITO backside is marked, it is ultrasonically cleaned in 2% ITO cleaning solution, deionized water, isopropanol, and ethanol for 15 minutes in sequence, dried at 60 °C, and then treated with ultraviolet ozone for 3 minutes.

[0072] A6-2 Hole transport layer: After filtering PEDOT:PSS, it is drop-coated on the surface of ITO, spin-coated at 5000 rpm for 30 s (film thickness ≈ 20 nm), annealed in air at 150 °C for 15 minutes, and transferred to a nitrogen glove box for standby.

[0073] A6-3 Solution preparation: The mixed solvent is prepared by mixing chlorobenzene and 2-bromothiophene in a volume ratio of 10-n:n; where n = 2, and then 4CzFCN is dissolved in this mixed solvent at a concentration of 8 mg / mL; TPBi is dissolved in chloroform containing 0.5 vol% 1-chloronaphthalene (9.6 mg / mL), and all solutions are stirred for ≥ 1 h before spin coating.

[0074] A6-4 Spin coating the active layer: The donor precursor solution and the acceptor precursor solution are spin-coated in sequence to obtain an active layer film of about 100 nm.

[0075] A6-5 Electron transport layer: After stirring the LiF / trifluoroethanol (1.0 mg / mL) solution at room temperature, it is spin-coated into a film at 3000 rpm.

[0076] A6-6 Electrode evaporation: Aluminum (thickness 100 nm) is evaporated in a vacuum of 5×10 -4 Pa, and the effective area of the device is 0.04 cm 2 .

[0077] The chemical formula of 4CzFCN is:

[0078] The chemical formula of TPBi is:

[0079] Comparative Example 2

[0080] The difference between Comparative Example 2 and Example 5 is that the solvent is chlorobenzene, and the others are the same as Example 5.

[0081] Effect Example

[0082] The photovoltaic parameters of the solar cells (devices) in the examples and Comparative Example 1 are shown in Table 1.

[0083] Table 1 Photovoltaic parameters of the D18 / L8-BO system based on different volumes of 2-BrTh

[0084]

[0085] It is not difficult to see from the data in Table 1 that the introduction of the 2-BrTh solvent can significantly improve the device efficiency. The device of Comparative Example 1 obtained a V of 0.910V OC , 25.82 mA cm -2 of J SC , 77.44% of FF and 18.21% of PCE. After adding 10% of 2-BrTh to the CB, the device of Example 1 achieved a PCE of 18.92%, mainly due to the increase in JSC, from 25.82 mA cm -2 increasing to 26.12 mA cm -2 . When the addition amount was gradually increased to 20%, the J of the device of Example 2 SC increased to 26.66 mA cm -2 , and the most obvious improvement was the FF, reaching 80.14%, so the PCE increased to 19.52%. Then, the volume fraction of 2-BrTh was further increased to 30%. The J of the device of Example 3 SC could be stabilized at 26.62 mA cm -2 , but the FF began to decrease slightly, to 79.85%, but the PCE could reach 19.37%. Finally, when the volume fraction of 2-BrTh was increased to 40%, the FF of the device of Example 4 decreased to 78.12%, and the J SC could only reach 26.17 mA cm -2 , and the finally obtained best efficiency reached 18.66%. It was found that the PCE of the device treated with 2-BrTh was higher and more concentrated.

[0086] We also carried out EQE tests. As Figure 1 shown, the device of Example 2 (denoted as D18(CB + 2-BrTh) / L8-BO(CF)) had a significant improvement in the range of 450 - 800 nm compared with Comparative Example 1 (denoted as D18(CB) / L8-BO(CF)).

[0087] Stability analysis of the solar cells (devices) of the examples and Comparative Example 1

[0088] The device stability of organic solar cells is an important criterion for measuring whether they can be commercialized. MPP measurements were carried out to study the effect of 2-BrTh on the device stability. [[ID= Shows the performance of the unencapsulated devices based on Comparative Example 1 (denoted as D18(CB) / L8-BO(CF)) and Example 2 (denoted as D18(CB + 2-BrTh) / L8-BO(CF)) under continuous illumination of 100 mW cm -2 .

[0089] As ​As described above, Example 2 exhibits better light stability than Comparative Example 1, retaining 91% of the initial PCE after 200 hours of continuous illumination (the polymer donor D18 treated with CB retains 86% after 200 hours). The improvement in PCE after modification confirms our above discussion. Once again, it shows that treating the polymer donor D18 layer with 2-BrTh can effectively alleviate the attenuation rate of OSCs.

[0090] Charge carrier transport characteristics:

[0091] To study the charge recombination behavior of the D18 / L8-BO system, the dependencies of the open-circuit voltage and short-circuit current on light intensity were analyzed. In the curve of V OC versus light intensity, we fitted the points corresponding to the open-circuit voltage and light intensity, as shown in ​ (a). Compared with the slope of 1.66kT / q for the device of Comparative Example 1, the slope of the device of Example 2 is 1.20kT / q, indicating that using 2-BrTh as a dual-solvent strategy can significantly reduce the slope of the device. At this time, the recombination in the device is mainly bimolecular recombination, indicating that the addition of the 2-BrTh solvent inhibits trap-assisted recombination. In other words, the addition of the 2-BrTh solvent helps to reduce trap-assisted recombination.

[0092] After determining the recombination mode of the device, we used the empirical formula Jsc∝(P light ) a to fit the values corresponding to the short-circuit current and light intensity to obtain the slope. Among them, the value of a represents the factor of bimolecular recombination. When the value of a approaches 1, it means that the bimolecular recombination in the D18 / L8-BO system is inhibited and the device performance is better. As shown in ​ (b), the value of a for the device of the example is 0.968, and the value of a for the device of Comparative Example 1 is 0.999. The value of a gradually increases, indicating that the bimolecular recombination of the device of Comparative Example 1 is effectively inhibited. The analysis results of the dependencies of V OC and J SC on light intensity show that the device of D18(CB + 2-BrTh) / L8-BO exhibits lower bimolecular recombination and trap-assisted recombination phenomena, thus showing higher photoelectric conversion efficiency.

[0093] Subsequently, the carrier lifetime in the device was measured using the TPV technique, and the charge extraction behavior of the device was tested using the TPC technique. Based on the measured carrier lifetime duration and charge extraction time, the device performance was evaluated. From the results of TPC, as shown in ​ (c), the charge extraction time of the device of Comparative Example 1 is 0.25 μs, and the charge extraction time of the device of Example 2 is 0.40 μs. From the results of TPV, as shown in ​As shown in (d), the carrier lifetime of the device in Example 2 is 1.64μs, which is longer than the carrier lifetime (1.32μs) of the device in Comparative Example 1. In addition, the device with 2-BrTh added exhibits the characteristics of extended carrier lifetime and shortened charge extraction time, which is beneficial to improving the J SC Quite beneficial.

[0094] We further used the Photo-CELIV technique to more closely investigate the charge recombination process in the device, where the current density-voltage curves as a function of the delay time are plotted on ​ In (ac), the γ values of the devices of Example 2 and Comparative Example 1 are 0.706 and 0.639 respectively, which indicates that the possibility of trap-assisted recombination in the 2-BrTh device is even smaller. SC The current density-voltage curve can be measured by Photo-CELIV technology, and the mobility can be calculated by the following formula:

[0095]

[0096] In the formula, d is the thickness of the dielectric, A is the voltage rise rate, Δj is the maximum value of the extracted current, and t max is the time when the current reaches its maximum value. The mobility of the device in Example 2 is 6.30×10 -5 cm 2 / Vs, compared with 6.13×10 -5 cm 2 / Vs has been significantly improved.

[0097] like ​ (d) We further measured the density of trap states (DOS). The data obtained from the capacitance frequency (Cf) and forward bias capacitance voltage (CV) measurements were fitted to obtain Nt using the following formula.

[0098]

[0099] In the formula, Nt is the total trap density, Et is the center of the trap state density (DOS), and δ is the disorder parameter. The trap density Nt value of the device ranges from 1.39×10 16 cm -3 Down to 1.14×10 16 cm -3 As shown in the above tests, the introduction of 2-BrTh can significantly suppress traps and generate lower energy disorder, thereby enhancing the carrier transport capability, which is also the reason for the improvement of FF parameters.

[0100] Preparation and Characterization of the Active Layer Thin Film

[0101] The boiling points of CB and 2-BrTh are 132 °C and 150 °C respectively. To more intuitively understand the effect of the dual-solvent strategy, we used CB and CB + 20% vol 2-BrTh as mixed solvents to dissolve D18. As ​ shown, we adopted the method of heating and stirring to accelerate the dissolution of D18. After heating at 110 °C for 30 min, there was still a certain solid form of D18 in the D18 with CB as the solvent. Compared with CB + 20% vol 2-BrTh, the solubility of D18 in CB was poor. Therefore, we speculated that dissolving a certain amount of high-boiling-point 2-BrTh in CB could improve the dissolution of D18, which was more conducive to the spin-coating of the upper-layer acceptor L8-BO, promoted charge transport, promoted the dissolution of D18, improved the crystallinity of the donor, and optimized the morphology of the active layer.

[0102] To further study the role of 2-BrTh in the active layer, we first tested the D18(CB) film and the D18(CB + 2-BrTh) film.

[0103] The preparation methods of the D18(CB) film and the D18(CB + 2-BrTh) film are as follows:

[0104] Chlorobenzene and 2-bromothiophene were mixed according to a volume ratio of 10 - n:n (0 < n ≤ 10) to obtain a mixed solvent; the mixed solvent was mixed and stirred with D18 powder to obtain a donor precursor solution; chloroform (CF) and L8-BO powder were mixed and stirred to obtain an acceptor precursor solution;

[0105] When n = 0, the donor precursor solution was spin-coated to prepare the D18(CB) thin film;

[0106] When n = 2, the donor precursor solution was spin-coated to prepare the D18(CB + 2-BrTh) thin film;

[0107] ​ (a) and (b) show the UV-visible absorption curves of the D18(CB) film and the D18(CB + 2-BrTh) film. It can be seen from the figure that compared with the D18 thin film without 20% vol 2-BrTh, the maximum absorption wavelength of the D18 thin film treated with CB was at 586.7 nm, and the maximum absorption wavelength of D18(CB + 2-BrTh) was at 582.3 nm, showing a blue shift of about 4 nm. This indicates that the addition of high-boiling-point 2-BrTh improved the molecular arrangement of D18. This further confirmed the ability of the introduction of 2-BrTh to regulate the morphology of the active layer and could obtain a more ideal phase separation size. ​(c) Spectral tests on two layered thin film systems of D18(CB) / L8-BO(CF) and D18(CB+2-BrTh) / L8-BO(CF).

[0108] Preparation methods for D18(CB) / L8-BO(CF) film, D18(CB+2-BrTh) / L8-BO(CF) film, and L8-BO(CF) film:

[0109] Chlorobenzene and 2-bromothiophene were mixed in a volume ratio of 10-n:n (0 < n ≤ 10) to obtain a mixed solvent; the mixed solvent was mixed and stirred with D18 powder to obtain a donor precursor solution; chloroform (CF) and L8-BO powder were mixed and stirred to obtain an acceptor precursor solution;

[0110] When n = 0, the donor precursor solution and the acceptor precursor solution were spin-coated in sequence to prepare a D18(CB) / L8-BO(CF) thin film;

[0111] When n = 2, the donor precursor solution and the acceptor precursor solution were spin-coated in sequence to prepare a D18(CB+2-BrTh) / L8-BO(CF) thin film;

[0112] The acceptor precursor solution was spin-coated to prepare an L8-BO(CF) thin film; after data normalization, it was found that the acceptor L8-BO in D18(CB+2-BrTh) / L8(CF) had higher light absorption, indicating that after D18 was treated with CB+2-BrTh, it also had a certain impact on the upper layer of L8-BO.

[0113] ​ (d) The presented is the PL test of the thin film formed by dissolving the polymer donor D18 in different solvents. When 50 nm was used as the excitation wavelength, for the thin film composed of D18 dissolved in CB solvent, its maximum emission peak was approximately at the position of 628 nm, and there was a shoulder peak near 670 nm. The normalized curves are also shown in ​ (a) and (b). It can be visually seen from the figure that after normalization, for the thin film formed by D18 dissolved in the CB+2-BrTh dual solvent system, the shoulder peak at 680 nm was more prominent. Subsequently, the device prepared by spin-coating optimized the arrangement state of D18 molecules, making the molecular arrangement more ordered, and thus had a favorable impact on both the exciton dissociation process and the charge transport process.

[0114] Considering that the compatibility between donor D18 and acceptor L8-BO is crucial for regulating the morphology of the active layer of organic solar cells fabricated by sequential deposition method, the surface free tensions of the donor and acceptor under different treatment conditions were studied. Calculated by the Owens-Wendt (OW) method, the surface energy (γ) was decomposed into the dispersion component (γ d ) and the polar component (γ p ). By measuring the contact angles (θ) of two liquids with known surface tension components (such as water and diiodomethane), a set of simultaneous equations were established for solution. The formula is:

[0115]

[0116] γ = γ d + γ p

[0117] The water contact angles and organic solvent (diiodomethane) contact angles of D18(CB) film, D18(CB + 2-BrTh) film and D18(CB) / L8-BO(CF) film, D18(CB + 2-BrTh) / L8-BO(CF) film, L8-BO(CF) film were measured respectively, as shown in Table 2.

[0118] Table 2 Contact angle and surface free tension data of donor and acceptor thin films under different treatment conditions

[0119] ​ ​ ​ ​ <![CDATA[γ(mNm -1 )]]> D18 ​ 102 50 33.55 D18 ​ 105 59 34.74 ​ ​ 100 52 33.83 ​ ​ 98 62 36.22 ​ ​ 91 40 39.83

[0120] For the D18(CB) film, the water contact angle and diiodomethane contact angle were 102° and 50° respectively. After adding 2-BrTh, the water contact angle and diiodomethane contact angle of the film decreased to 105° and 59° respectively, and the corresponding surface free tensions were 33.55 mN m -1 and 34.74 mN m -1 . At the same time, for the L8-BO film, the water contact angle and diiodomethane contact angle of the pure film were 91° and 40° respectively, and its surface free tension was 39.83 mN m -1 . For the D18(CB) / L8-BO(CF) film, the water contact angle and diiodomethane contact angle were 100° and 52° respectively. After adding 2-BrTh, the water contact angle and diiodomethane contact angle of the D18(CB + 2-BrTh) / L8-BO(CF) film decreased to 98° and 62° respectively, and the corresponding surface free tensions (γ) were 33.83 mN m -1 and 36.22 mN m -1 . The Flory-Huggins interaction parameter χ can be obtained from the equation Calculation was used to estimate the thermodynamic intermolecular compatibility between the donor and acceptor materials. The interaction parameter was calculated based on the surface energies of the donor and acceptor. When CB and 2-BrTh were used to dissolve the donor and spin-coated into a film, the χ value increased to 1.06 K. The increase in the χ value means that the miscibility between the donor and acceptor decreased slightly, and the phase separation degree of the film intensified. That is to say, after using the double-solvent method, the film morphology of the donor D18 was optimized first.

[0121] To study the changes in film-forming kinetics, we used the change in the peak position in in-situ ultraviolet-visible spectroscopy to monitor the film-forming process of the donor and acceptor, which mainly included four systems: D18(CB), D18(CB+2-BrTh), D18(CB) / L8-BO(CF), and D18(CB+2-BrTh) / L8-BO(CF), as ​ and 8 shown.

[0122] From ​ (a) and (b), we first studied the film-forming kinetics of D18(CB). For D18(CB), the time from the solution state to the film state was about 68 ms, and the absorption wavelength in the final stable film state was about 584.8 nm. For D18(CB+2-BrTh), the time from the solution state to the film state was about 119 ms, and the absorption wavelength in the final stable film state was about 582.7 nm. Compared with D18(CB), D18(CB+2-BrTh) had a longer film-forming time. This was mainly because under the double-solvent strategy, 2-BrTh had a higher boiling point and was difficult to volatilize with CB, so it took a longer time to form a film. And D18 dissolved in CB was prone to excessive aggregation (which could also be seen from AFM), resulting in a significant shortening of the phase separation time. We also extracted the curves of the absorption intensity of D18 versus time in the first 300 ms before film formation under different solvents, as ​ (e) and (f) shown.

[0123] To study the change in the film-forming time of D18 under different solvent treatments with the non-fullerene acceptor L8-BO. After D18 was completely formed into a film, we uniformly dropped the solution of the acceptor L8-BO at 500 ms. The relationship between the absorption wavelength and time of film formation was as ​As shown in (a) and (b). Then, we extracted the curves of absorption wavelength and absorption intensity every 10 ms. For D18(CB), at 500 ms, there was only the absorption peak of D18(CB) in the stable state. With the dropwise addition of L8-BO in the solution state, the absorption peak of L8-BO in the solution state began to appear. The film-forming time of the receptor L8-BO on D18(CB) was 28 ms, and the absorption wavelength was stable at 788.6 nm. In addition, the intensity of the absorption peak of D18(CB) also began to change, increasing from the original 0.34 to 0.45. However, the film-forming change of D18(CB+2-BrTh) / L8-BO(CF) was different from that of D18(CB) / L8-BO(CF). Spin-coating the receptor L8-BO on D18(CB+2-BrTh) would have a relatively slow film-forming time of 40 ms, and the absorption wavelength was stable at 788.9 nm. At the same time, after the film of L8-BO was formed stably, the absorption intensity of D18(CB) increased from 0.45 to 0.57 of D18(CB+2-BrTh), improving the light utilization rate.

[0124] We then further studied the surface of the active layer of the D18 / L8-BO system, as ​ and 10 shown. In addition, compared with other composite films, the roughness of the D18(CB+2BrTh) / L8-BO(CF) film was 1.61 nm, which was closer to the surface roughness of the pure receptor L8-BO film of 0.86 nm. This phenomenon reflected that in this case, there were more receptors distributed in the area of the active layer surface close to the electron transport layer. And the distribution of more receptors at this position promoted the process of charge transport and collection.

[0125] In summary, in this application, chlorobenzene and 2-bromothiophene were used as solvents to prepare the active layer. By precisely regulating the microstructure of the donor layer, efficient exciton dissociation and charge collection inside the device were achieved, significantly improving the overall performance of the D18 / L8-BO system organic solar cell.

[0126] We also applied 2Br-Th as a solvent to the performance of solution-processed organic light-emitting diode (OLED) devices (Example 5). The structure of the OLED device was as ​ shown, adopting the classic device structure ITO / PEDOT:PSS / 4CzFCN / TPBi / LiF / Al. Among them, the blue light material 4CzFCN layer was deposited on the PEDOT:PSS layer by solution spin-coating, while the electron transport layer TPBi and the hole blocking layer LiF were prepared on the 4CzFCN layer by thermal evaporation.

[0127] ​The device prepared with 2Br-Th showed an external quantum efficiency (EQE) of 1.62%, significantly higher than 0.88% of the device with CB solvent. The improvement in luminescence performance and efficiency can be attributed to the suppression of the aggregation tendency of the 4CzFCN film by the 2Br-Th solvent, as ​ , ​ Figure AFM shows the AFM images of the films prepared by dissolving 4CzFCN in CB and 2Br-Th solvents and spin-coating. It can be seen from the figure that the root mean square (RMS) surface roughness of the film prepared with 2Br-Th as the solvent is 0.89 nm, forming a more uniform and flat film, while the film prepared with CB solvent shows a rough surface with an RMS of 2.58 nm. This flat morphology is beneficial to excellent charge transport kinetics, while the rough morphology of the CB film leads to serious leakage current phenomena.

[0128] In summary, the improved luminescence performance and efficiency demonstrate the great application potential of the SMII strategy in various organic optoelectronic devices.

[0129] Importantly, it should be noted that the construction and arrangement of the present application shown in multiple different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those skilled in the art who refer to this disclosure should easily understand that many modifications are possible without substantially departing from the novel teachings and advantages of the subject matter described in this application (e.g., changes in the dimensions, scales, structures, shapes and proportions of various elements, and parameter values (such as temperature, pressure, etc.), installation arrangements, use of materials, colors, orientations, etc.). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of the element may be inverted or otherwise changed, and the nature, number or position of discrete elements may be altered or changed. Therefore, all such modifications are intended to be included within the scope of this application. The order or sequence of any process or method steps may be changed or reordered according to alternative embodiments. In the claims, any "means-plus-function" clause is intended to cover the structures that perform the recited function described herein, and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of this application. Therefore, this application is not limited to a specific embodiment, but extends to various modifications that still fall within the scope of the appended claims.

[0130] In addition, in order to provide a concise description of the exemplary embodiments, not all features of the actual embodiments may be described (i.e., those features that are not relevant to the currently considered best mode of implementing this application or those that are not relevant to the implementation of this application).

[0131] It should be understood that, in the development of any actual implementation, such as in any engineering or design project, a large number of specific implementation decisions can be made. Such development efforts may be complex and time-consuming, but for those of ordinary skill in the art who benefit from this disclosure, without undue experimentation, such development efforts will be routine work of design, manufacture, and production.

[0132] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application, and they should all be covered within the scope of the claims of the present application.

Claims

1. A preparation method of an active layer based on the regulation of polymer aggregation structure, characterized in that It includes the following steps: S1 Configure the donor precursor solution; the solvent of the donor precursor solution is prepared by mixing chlorobenzene and 2-bromothiophene in a volume ratio of 10-n:n; where 0 < n ≤ 10. S2 Configure the acceptor precursor solution; S3 Spin-coat the donor precursor solution and the acceptor precursor solution in sequence to obtain an active layer thin film.

2. The preparation method of the active layer according to claim 1, wherein: The donor includes D18 and 4CzFCN; the acceptor includes L8-BO and TPBi.

3. The preparation method of the active layer according to claim 1, wherein: The concentration of the donor in the donor precursor solution is 7.6 - 8.4 mg / mL, and the concentration of the acceptor in the acceptor precursor solution is 9 - 10.2 mg / mL; And / or, the solvent of the acceptor precursor solution includes chloroform; And / or, the acceptor precursor solution further contains 0.5 vol% 1-chloronaphthalene.

4. The method for preparing the active layer according to claim 1, wherein: The mixing and stirring temperature in step S1 is 100 °C; the mixing and stirring temperature in step S2 is room temperature.

5. The preparation method of the active layer according to claim 1, characterized in that: The thickness of the photoactive layer is 90 - 110 nm.

6. An active layer prepared by the method according to any one of claims 1 - 5.

7. An organic solar cell, characterized in that: The organic solar cell is composed of a conductive substrate, a hole transport layer, a photoactive layer, an electron transport layer, and a metal electrode, and the photoactive layer is the active layer according to claim 7.

8. The organic solar cell according to claim 8, characterized in that: The conductive substrate is an ITO substrate; the hole transport layer is composed of PEDOT:PSS; the active layer is composed of D18 and L8-BO; the electron transport layer is composed of PDIN; the metal electrode is an Ag electrode.

9. An organic light-emitting diode device, characterized in that, The organic light-emitting diode device is composed of a conductive substrate, a hole transport layer, an active layer, an electron transport layer, and a metal electrode; the active layer is the active layer according to claim 7.

10. The organic light emitting diode device according to claim 9, wherein The conductive substrate is an ITO substrate; the hole transport layer is composed of PEDOT:PSS; the active layer is composed of 4CzFCN and TPBi; the electron transport layer is composed of LiF; the metal electrode is an Al electrode.

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